Ozone-Based Disinfecting Device Comprising a Flow Sensor

ABSTRACT

An ozone-based disinfecting device is provided comprising a mixer having a generally hollow body with a water inlet for water under pressure, a spray nozzle for generating a generally conical spray of water introduced by way of the water inlet, a contact chamber communicating with a gas inlet for ozone rich gases, and an outlet aperture from the contact chamber that is coaxial with the spray nozzle and spaced apart therefrom. An electronic flow sensing device senses the extent of the flow of water through the spray nozzle according to vibration caused by water flowing through the mixer. The electronic flow sensing device is preferably located in a pocket formed in the mixer and preferably comprises a piezoelectric sensor embedded at least around its periphery in a settable material. A preferred construction of the mixer is also described.

REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/116,533 filed Nov. 11, 2013, which is a U.S. National StageApplication of International Application No. PCT/IB2012/52355 filed May11, 2012, which claims priority to South African Patent Application No.2011/03473 filed May 12, 2011, the entirety of each of which isincorporated by reference.

FIELD OF THE INVENTION

This invention relates to an ozone-based disinfecting device of thegeneral nature in which the device, in use, generates a water sprayhaving an effective and appropriate quantity of ozone embodied therein.More particularly, the invention relates to an ozone-based disinfectingdevice that is suitable for use in relation to food, although it may beused in many other applications.

Still more particularly, the invention relates to a disinfecting deviceof the general nature described in our earlier published internationalpatent application WO 2010/001279.

BACKGROUND TO THE INVENTION

Microbial outgrowth is a primary concern in the food processing industryand amongst consumers. The presence of pathogenic microorganisms on foodproducts can potentially lead to food-borne outbreaks of disease.

Chlorine-based chemicals such as sodium hypochlorite, calciumhypochlorite, sodium dichloroisocyanurate and quaternary ammoniumcompounds have been employed for disinfecting food products in the past.However, chlorine is most effective at a pH of 6 to 8, and becomes lesseffective outside of this pH range. Also, chlorine can produce toxicbyproducts that are harmful to human health, such as chloramines andtrihalomethanes.

As a result of this, the European Union has imposed a bar against theuse of chlorine compounds for disinfecting food produce, as specified bythe EU Directive 2092/91. There has consequently been a concerted effortto improve technology employing non-chlorine based products for thetreatment of food products to disinfect them. This has resulted in anincreased interest in the disinfecting properties of ozone. The use ofozone for disinfecting food has been approved by the United States Foodand Drug Administration (FDA).

It is noted that ozone is reported to have about 1.5 times the oxidizingpotential of chlorine with contact times for the anti-microbial actionof ozone being typically four to five times less than that of chlorine.

Ozone has been shown to be a highly reactive oxidant that is capable ofkilling microorganisms such as bacteria as well as reacting with otherchemicals such as pesticides and herbicides. Of course, a majoradvantage of ozone is its natural decomposition into oxygen and thus itsuse in disinfecting food products is highly beneficial as it decomposesinto a non-toxic gas. It therefore does not impart odour to, or taint,food products and no residual compounds or toxic residue remain. Rinsewater can be discharged to the environment or used for otherapplications without additional treatment or decontamination.

In prior art disinfecting processes known to applicant to use ozone,venturi injection systems and bubble diffusers have been used to mixozone into water. In the case of venturi injectors, water is forcedthrough a convergent conical body, initiating a pressure differentialbetween the inlet and the outlet of the system. This creates a vacuuminside the body of the injector, thereby initiating a flow of ozone richair through a suction port.

As regards bubble diffusers, ozone rich air is emitted in bubblesbeneath the surface of the water. Irrespective of the problems furtheridentified below, bubble diffusers suffer from an inherent disadvantagein that diffuser holes frequently become fouled over time therebydecreasing the efficiency of the system.

In both instances, ozone is dissolved into the water, typically from anozone rich air, and an appreciable proportion of the sterilizing abilityof the ozone may be spent in sterilizing the water itself. This leaves areduced amount of ozone available for effective disinfecting of theultimate target that may be fresh produce, for example.

Furthermore, these prior art systems appear to allow free gaseous ozoneto be released into the atmosphere in higher concentrations than ispermitted by regulatory standards. It is to be noted that free ozone inthe air is harmful when it exceeds predetermined concentrations.

In this regard it is to be noted that in the European Union, the currenttarget value for ozone concentrations is reported to be 120 μg/m³ whichis about 60 nmol/mol. This target applies to all member states inaccordance with Directive 2008/50/EC although there is no date set forformalizing this as a requirement and it is treated as a long-termobjective. In the USA, in May 2008, the Environmental Protection Agency(EPA) lowered its ozone standard from 80 nmol/mol to 75 nmol/mol. Thiswas done in spite of the fact that the Agency's own scientists andadvisory board had recommended lowering the standard to 60 nmol/mol. TheEPA has developed an Air Quality Index to help explain air pollutionlevels to the general public and presently the current standardsdescribe an eight-hour average ozone mole fraction of 85 to 104 nmol/molas “unhealthy for sensitive groups”; 105 nmol/mol to 124 nmol/mol as“unhealthy”; and 125 nmol/mol to 404 nmol/mol as “very unhealthy”. TheWorld Health Organization recommends 51 nmol/mol.

Excess ozone in the air is therefore quite undesirable and it isimportant that any disinfecting device using ozone as its activedisinfecting medium should not release any appreciable quantities ofozone into the atmosphere, whilst providing an effective concentrationto destroy target bacteria etc.

In our earlier international patent application identified above, theproposal for sensing water flow through a mixer was to monitor theincrease in pressure in the mixer when water was applied under pressureto the mixer. This expedient did not operate effectively and alternativecontrols needed to be investigated.

SUMMARY OF THE INVENTION

In accordance with this invention there is provided an ozone-baseddisinfecting device comprising a mixer having a generally hollow bodywith a water inlet for water under pressure; a spray nozzle forgenerating a generally conical spray of water introduced by way of thewater inlet; a contact chamber communicating with a gas inlet for ozonerich gases; an outlet aperture from the contact chamber with the outletaperture being coaxial with the spray nozzle and spaced apart therefrom,and a flow sensing device for sensing the extent of flow of waterthrough the spray nozzle, the ozone-based disinfecting device beingcharacterized in that the flow sensing device is an electronic flowsensing device for sensing vibration caused by a flow of water throughthe mixer.

Further features of the invention provide for the electronic flowsensing device to be located in a pocket provided in the mixer body; forthe electronic flow sensing device to include a piezoelectric sensor andan appropriate associated circuit for generating a signal indicative ofthe rate of flow of water through the mixer; and for the piezoelectricsensor to be embedded in a settable material and have the general shapeof a disc that has a thin smaller diameter compressible disc adheredconcentrically to both surfaces of the sensor disc with the outerdiameter of the piezoelectric sensor firmly embedded in the settablematerial and wherein a small hole in the centre of one disc provides forthe settable material to contact the piezoelectric sensor in the centralregion on the one side thereof.

Still further features of the invention provide for an associatedcircuit to be carried on a printed circuit board housed within the mixerbody; for the printed circuit board to be housed in a pocket in themixer body; for the flow sensing device and an associated circuit to bearranged to activate and deactivate an ozone generator operativelyconnected to the gas inlet for ozone rich gases; for a signal outputtedby the flow sensing device and associated circuit to operativelyactivate and deactivate a fan supplying air to the ozone generator withactivation of the fan being effected before activation of the ozonegenerator takes place and deactivation of the fan being effected afterdeactivation of the ozone generator takes place; and for the fan to becapable of running at different speeds dependent on the flow rate ofwater through the spray nozzle.

Additional features of the invention provide for the diameter of theoutlet aperture to correspond substantially to the diameter of theconical spray at that position so that substantially no free spaceexists between the outside of the conical spray and the periphery of theoutlet, in use; for the contact chamber itself to have a largercross-sectional size than the diameter of the outlet aperture; and forthe gas inlet for ozone rich gases to have an axis parallel to, butlaterally offset from, that of the water inlet with a gas inlet chambermerging laterally with the contact chamber.

The mixer body is preferably composed of a first part in the form of ashroud defining the outlet aperture that receives, in an open endopposite the outlet aperture, a second part defining the water inlet,gas inlet and a pocket for receiving the electronic flow sensing devicefor sensing the extent of flow of water through the spray nozzle withthe second part of the body being received in the open end of the shroudpart of the body in plug-like manner.

The water inlet is preferably configured as a screw threaded socket forapplication directly to a complementarily screw threaded spout of a tapor other tubular water dispensing item.

In accordance with a second aspect of the invention there is provided anozone-based disinfecting device comprising a mixer as defined above; anozone generator operatively connected to the gas inlet for ozone richgases in the mixer; and a control circuit connected to the flow sensingdevice and any associated circuit, wherein the control circuit isconfigured to activate the ozone generator once a signal is receivedfrom the flow sensing device and any associated circuit corresponding toa minimum flow rate of water through the mixer that is required todevelop a suitable spray cone of water occupying the outlet aperturefrom the contact chamber and to deactivate the ozone generator once thesignal received corresponds to less than said minimum flow rate.

It is to be noted that practice of the present invention results inozone rich gases becoming entrained with multitudinous water droplets ofthe spray and it is believed that the ozone adheres itself in some way,possibly electromagnetically or electro-statically, to the surface ofthe water droplets without any appreciable proportion of the ozonebecoming dissolved in the water. This theory explains the practicalmeasurements taken to date that indicate that more ozone is carried bythe water than would normally be soluble in it. Tests conducted to datehave also revealed that there is substantially no free ozone in the airsurrounding the disinfecting spray and there is little or no ozoneremaining in the spent water. Practice of the invention apparentlyapproaches optimal use of ozone and enables it to be highly effective inits disinfecting activity.

Whilst the mechanism of the attachment or otherwise of ozone moleculesto the water droplets of the spray is not yet fully understood, or fullyresearched technically, tests conducted to date indicate that thedroplet size developed by the spray is preferably between 10 and 50 μmand the water spray cone preferably has a cone angle of between 35° and45°. Also, the flow developed by the fan and the reduction in pressurecreated by the flow of the conical spray out of the outlet aperture, issuch that a slightly negative pressure, of the order of 10 mm of water(100 Pa), is maintained within the contact chamber. In this regard,further tests will be directed at establishing whether or not it ispractical to do away with the fan completely and this will dependlargely on the negative pressure that is generated within the contactchamber and the nature of the flow path through the ozone generator tothe mixer.

In order that the above and other features of the invention may becomemore apparent, one embodiment embracing all of the different aspects ofthe invention will now be described with reference to the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a schematic illustration of the various components of anozone-based disinfecting device according to the invention;

FIG. 2 is an illustration of the ozone generator used in the deviceillustrated in FIG. 1 with its cover removed;

FIG. 3 is a similar illustration of the ozone generator with certaincomponents removed in order to reveal others;

FIG. 4 is an exploded perspective view of the mixer illustrated in FIG.1;

FIG. 5 is a sectional elevation of the mixer illustrated in FIGS. 1 and4;

FIG. 6 is a plan view of the mixer;

FIG. 7 is a block circuit diagram of the circuit of the piezoelectricdetection circuit; and,

FIG. 8 is a graph showing the variation of output from the piezoelectricsensor and associated circuit and to the water pressure as against flowrate through the mixer.

DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS

In the embodiment of the invention illustrated in the drawings, anozone-based disinfecting device comprises a mixer (2) having a generallyhollow body with a screw threaded socket (3) as a water inlet for waterunder pressure with the socket being adapted for direct connection to ascrew threaded outlet from a water supply tap (4) or some other watersupply device having a tubular outlet.

A gas inlet (5) for ozone rich gases has its axis parallel to, butlaterally offset from, that of the water inlet with a gas inlet chamber(6) merging laterally with an otherwise generally cylindrical contactchamber (7) surrounding the water inlet. The mixer has a spray nozzle(8) that embodies a swirler (9) (see FIG. 4) for generating a generallyconical spray (11) of water introduced by way of the water inlet (seeFIG. 5) such that a conical spray is directed into the contact chamberand towards a coaxial reduced diameter outlet aperture (12) spaced aparttherefrom. The contact chamber itself has a larger cross-sectional sizethan the diameter of the outlet aperture. The spray nozzle is coaxialwith the water inlet and the nozzle itself is located generallycentrally in the contact chamber.

The diameter of the outlet aperture corresponds substantially to theouter diameter of the conical spray at that distance from the nozzle sothat substantially no free space exists between the outside of theconical spray and the periphery of the outlet. In fact, in use, theouter perimeter of the conical spray may be cut off slightly by theperiphery of the outlet aperture although care should be taken that theextent of this should not cause larger droplets to coalesce on theperimeter of the outlet.

As regards the construction of the mixer body, it is convenientlycomposed of a first part (15) in the form of a shroud defining theoutlet aperture and an open end opposite the outlet aperture thatreceives a second part (16) defining the water inlet, gas inlet, as wellas a pocket (17) between the water inlet and gas inlet. The lateralmerging of the gas inlet chamber and contact chamber, in this instance,takes place on the sides and beneath the pocket.

The second part of the body is received in the open end of the shroudpart of the body in plug-like manner, as will be most apparent from FIG.4 of the accompanying drawings. Both the first and second parts of themixer body may be injection moulded or die cast from suitable ozoneresistant material and the two parts may be permanently sealed togetherin any suitable manner including ultrasonic welding, solvent welding andadhesive. The opening to the pocket may be closed by a suitable closure(18) that may have its own flexible cord collar (19) as shown in FIG. 4.

The mixer includes a flow sensing device in the form of a piezoelectricsensor (21) that is connected to an associated circuit in the form of anelectronic signal generating printed circuit board (22) that serves toamplify signals generated by the piezoelectric sensor and provide anoutput appropriate for operating a control circuit that is describedfurther below.

In order to ensure that the piezoelectric sensor is activated adequatelyby the vibration created by water passing through the mixer, thepiezoelectric sensor itself, as well as its associated circuit in theform of the printed circuit board (22), are received in the pocket (17)in the mixer body and the remaining space within the pocket is filledwith a suitable settable material. The settable material will thusensure that vibrations generated are properly transferred to thepiezoelectric sensor.

In one successful arrangement of the piezoelectric sensor it has theshape of a disc with a thin smaller diameter compressible, in thisinstance foam, disc (23) adhered concentrically to both surfaces of thesensor. The smaller outer diameter of the foam discs enables the outerperiphery of the piezoelectric sensor to become firmly embedded in thesettable material. A small hole (24) (see FIG. 4) in the centre of thefoam disc that is closer to the socket allows the settable material tocontact the piezoelectric sensor in the central region on the one sidethereof. The effect is that the piezoelectric sensor, being firmly heldaround its periphery and excited by the small pillar (indicated bynumeral (24 a) in FIG. 5) of settable material occupying the small hole(24), exhibits enhanced movement as a result of the fact that the foamallows the enhanced vibration of the piezoelectric sensor with acorrespondingly enhanced output therefrom.

Of course, the piezoelectric sensor is sensitive to vibration set up bywater as it passes through the nozzle and the vibration will vary,typically in frequency, with the flow rate of water. FIG. 8 is a graphillustrating the variation of flow rate with pressure and the outputfrom the piezoelectric sensor and associated circuit.

A microprocessor (41) is preferably included on the printed circuitboard and this enables other intelligent electronic sensors to beincorporated in the mixer circuit such as an infrared proximity sensor(42) for switching on the nozzle as well as for connection to a solenoidcontrolled water valve in which instance it can switch on the water flowitself. The sensor could thus be used for switching on ozonated flushingwater in a urinal, for example.

Simply for the sake of completeness, an example of an electronic circuitis illustrated in block diagram form in FIG. 7. It will be noted thatthe output from the piezoelectric sensor is firstly passed through a lowpass filter (43) and subsequently through an amplifier (44). Theamplified signal is passed through a high pass filter (45) followed by arectifier (46) and thereafter a low pass filter (47). Of course theelectronic circuit can include a light emitting diode (LED) (48) toindicate when the vibration sensor is excited. Also an additionalfunction of the LED in the mixer, or an additional LED, could be tocommunicate other information to a user such as to show timing intervalsby flashing every 15 seconds thereby aiding in dosing washed itemscorrectly. It can also show errors or unit faults by flashing sequencesof red (as opposed to green or blue) light. The printed circuit boardmay be provided with a communications connector (49) for connection tothe ozone generator is further described in what follows.

A separate ozone generator (25) of generally known construction and ofthe corona discharge type is operatively connected by way of a suitabletube (26) to the gas inlet (5) for ozone rich gases to the mixer. Theozone generator is, however, modified to operate in terms of thisinvention and houses a control circuit on a printed circuit board (27)(see FIG. 3) within the ozone generator housing.

The ozone generator is also connected to the mixer by way of acommunications cable (28) that serves to supply the printed circuitboard (22) and piezoelectric sensor (21) in the pocket within the mixerwith electrical energy at a low DC voltage and to convey signalsgenerated in response to the piezoelectric sensor to the control circuitin the ozone generator housing.

The control circuit incorporates a suitable transformer and rectifierfor connection by way of a suitable cable (31) to an electrical mainspower outlet supply. The control circuit is configured to activate acorona discharge ozone generator unit (32) once a signal is receivedfrom the mixer corresponding to a minimum predetermined flowrate ofwater through the mixer that will correspond to the development of aspray cone of water occupying the outlet aperture from the contactchamber. The control circuit similarly deactivates the ozone generatorunit once the signal received from the mixer corresponds to less thansaid minimum flow rate. It will be understood that, in this manner, thegeneration of ozone in the absence of an adequate flow of water throughthe mixer is avoided and ozone cannot be liberated into the atmospherein consequence.

The ozone generator, in this embodiment of the invention, also includesa variable speed centrifugal fan (33) for blowing air through the ozonegenerator and thence into the contact chamber of the mixer. Thecentrifugal fan has a substantially conventional centrifugal impeller(34) that is driven by a variable speed DC electric motor (35). Thevariable speed electric motor is controlled by the control circuit inresponse to signals received from the piezoelectric sensor such that thefan is activated before activation of the ozone generator takes placeand is deactivated after deactivation of the ozone generator takesplace.

In use a disinfecting spray of water carrying ozone as an activedisinfectant is generated with the spray passing through the contactchamber and out of the outlet aperture so that ozone is carried with thespray out of the outlet, as described above.

Operation of the disinfecting device is initiated by opening the tap tocause water to flow through the mixer and once the flowrate reaches aminimum level of, in this instance about 1.3 litres per minute, andpreferably between 1.6 and 2 litres per minute, the control circuit willfirstly switch on the DC motor that drives the fan to establish anairflow over the corona discharge unit (32) and, shortly afterwards, thehigh-voltage circuit of the corona discharge unit is energized to startgenerating ozone. This routine is followed to make sure that all of theozone that is generated is carried through to the mixer. The controlcircuit may also switch on an indicator light such as a blue LED toindicate that the air is flowing and that ozone is being generated.

As the tap is opened further the piezoelectric sensor in the nozzlecauses a signal of increased flow to be sent to the control circuitwhich adjusts the fan speed to increase the airflow in response to theincreased water flow. The disinfecting device thus has the ability tosense the rate of water flow and to supply an increased amount of ozoneto the mixer when the water flowrate increases.

The mixed ozone and water leave the nozzle in fine droplet/spray formand hit the target which is placed or handled in the water spray whereit is cleaned.

Thus the air is blown by the fan through the corona discharge unit at aspeed that is variable according to the signal received from thepiezoelectric sensor and its associated circuit. In this regard, it isto be noted that the piezoelectric sensor senses vibration created bythe passage of water through the swirler and nozzle of the mixer and theproperties of the vibrations will vary with the flowrate of waterthrough the mixer.

Simply by way of example, in test equipment employed, the followingpressures resulted in the stated flow rates of water and fan speeds withthe stated ozone content of the water:

Pressure Flow Rate Fan Speed Ozone Content Bar litres/min RPM ppm 2 1.32000 26 2500 29 3000 29 2.5 1.5 2000 26 2500 28 3000 28 3 1.7 2000 222500 25 3000 25 3.5 1.8 2000 22 2500 25 3000 25 4 1.9 2000 22 2500 233000 24

In spite of the foregoing, it is to be noted that it is also envisagedthat the slightly reduced pressure created in the mixing chamber byvirtue of the spray moving through it, may be enough to induce asatisfactory flow of air through the ozone generator thereby renderingthe fan and its associated controls not necessary with a consequentsaving in cost. However, in such an instance, the pressure of the watersupply should be relatively consistent within a predetermined practicalrange available from water mains.

Numerous variations and applications exist for the invention. Thus, forexample, a portable unit could be produced as a self contained shoulderslung unit with a water reservoir, a battery pack and an atomizinglance. A user could walk around an area sanitizing equipment for gyms orother large areas that cannot tollerate large volumes of water.

The nozzle could be attached to a dishwasher in order to supply aconstant sanitizing spray during a wash cycle. This arrangement mayallow a dishwasher to have its operating temperature reduced so as tosave electricity.

The nozzle could be attached to an overhead misting type of system tocreate a gentle cooling mist over fresh produce to cool and sanitize inmany situations such as a market, a transport vehicle, or any otherappropriate environment.

The device could be used in a tunnel with a conveyor and multiplenozzles could be spaced apart along the length of the tunnel for largevolume items that need to be sanitized. Such an arrangement could beused to sanitize fish packing crates or any other fresh produce packingcrates. This system could also be used to sanitize and remove pesticideson high volumes of fresh produce in packing houses.

The disinfecting device could be connected to a urinal so as to sprayozone enriched water into the urinal upon flushing. In this way bacteriaand odours could be reduced.

The unit may be an under-counter or wall mounted unit associated with adedicated wash basin, for example.

Numerous variations of the invention exist without departing from thescope hereof.

1. An ozone-based disinfecting device comprising a mixer having agenerally hollow body with a water inlet for water under pressure; aspray nozzle for generating a generally conical spray of waterintroduced by way of the water inlet; a contact chamber communicatingwith a gas inlet for ozone rich gases; an outlet aperture from thecontact chamber with the outlet aperture being coaxial with the spraynozzle and spaced apart therefrom, and a flow sensing device for sensingthe extent of flow of water through the spray nozzle, wherein the flowsensing device is an electronic flow sensing device for sensingvibration caused by a flow of water through the mixer includes apiezoelectric sensor and an appropriate associated circuit forgenerating a signal indicative of the rate of flow of water through themixer and wherein the periphery of the piezoelectric sensor is embeddedin a settable material.
 2. An ozone-based disinfecting device as claimedin claim 1 in which the electronic flow sensing device is located in apocket provided in the mixer body.
 3. An ozone-based disinfecting deviceas claimed in claim 1 in which the settable material includes a centralpillar of settable material in contact with the piezoelectric sensor. 4.An ozone-based disinfecting device as claimed in claim 1 in which thepiezoelectric sensor has the general shape of a disc that has a thinsmaller diameter compressible disc adhered concentrically to bothsurfaces of the sensor disc with the outer diameter of the piezoelectricsensor firmly embedded in the settable material and wherein a small holein the centre of one compressible disc provides for the settablematerial to contact the piezoelectric sensor in the central region onthe one side thereof.
 5. An ozone-based disinfecting device as claimedin claim 1 in which the associated circuit is carried on a printedcircuit board housed within a pocket in the mixer body.
 6. Anozone-based disinfecting device as claimed in claim 1 in which the flowsensing device and an associated circuit is arranged to activate anddeactivate an ozone generator operatively connected to the gas inlet forozone rich gases.
 7. An ozone-based disinfecting device as claimed inclaim 1 in which a signal outputted by the flow sensing device andassociated circuit operatively activates and deactivates a fan supplyingair to the ozone generator with activation of the fan being effectedbefore activation of the ozone generator takes place and deactivation ofthe fan being effected after deactivation of the ozone generator takesplace.
 8. An ozone-based disinfecting device as claimed in claim 7 inwhich the fan is capable of running at different speeds dependent on theflow rate of water through the spray nozzle.
 9. An ozone-baseddisinfecting device comprising a mixer having a generally hollow bodywith a water inlet for water under pressure; a spray nozzle forgenerating a generally conical spray of water introduced by way of thewater inlet; a contact chamber communicating with a gas inlet for ozonerich gases; an outlet aperture from the contact chamber with the outletaperture being coaxial with the spray nozzle and spaced apart therefrom,and a flow sensing device for sensing the extent of flow of waterthrough the spray nozzle, wherein the flow sensing device is anelectronic flow sensing device for sensing vibration caused by a flow ofwater through the mixer includes a piezoelectric sensor and anappropriate associated circuit for generating a signal indicative of therate of flow of water through the mixer wherein the mixer is composed ofa first part in the form of a shroud defining the outlet aperture and anopen end opposite the outlet aperture that receives a second partdefining the water inlet, gas inlet, and a pocket between the waterinlet and gas inlet with lateral merging of the gas inlet chamber andcontact chamber taking place beneath the pocket.
 11. An ozone-baseddisinfecting device as claimed in claim 1 in which the gas inlet forozone rich gases has an axis parallel to, but laterally offset from,that of the water inlet with a gas inlet chamber merging laterally withthe contact chamber.
 12. An ozone-based disinfecting device as claimedin claim 1 in which the mixer body is composed of a first part in theform of a shroud defining the outlet aperture that receives, in an openend opposite the outlet aperture, a second part defining the waterinlet, gas inlet and a pocket for receiving the electronic flow sensingdevice for sensing the extent of flow of water through the spray nozzlewith the second part of the body being received in the open end of theshroud part of the body in the manner of a plug.
 13. An ozone-baseddisinfecting device as claimed in claim 12 in which the water inlet isconfigured as a screw threaded socket for application directly to acomplementarily screw threaded spout of a tap or other tubular waterdispensing item.